Cementing agent for steel and iron



Dec 24, 1935. H. HANUscH l 2,025,050

CEMENTING AGENTFOR STEEL AND IRON v l Filed'Nov. s, 19314 Patented Dec.24, 1935 UNITED STATES ,PATENT ori-ICE CEMENTINGv AGENT FOR STEEL ANDIRON Hugo Hanlsch, Berlin, Germany, assigner to E. F. I

Houghton & Company, Philadelphia, Pa.

application November 3, 1931, serial No. 572,859l In Germany November 8,1930 claims.

ening process at the present time are characterized by a high content ofcyanide compounds. In order to increase the penetratingeiect of thecementing bath it had heretofore been necessary to increase the contentoi cyanide in the bath. In consequence of this, for instance, cementingsalts having a content of sodium cyanide of 45, 75 and even up to 98%are being put on the market by prominent concerns. v

However, on account of its poisonous qualities a salt bath of thiskindis a continuous source of danger.

In a general-way my' invention is based upon the discovery thatit ispossible to make cementing salt baths and solid cementing agents'(carburizers) which contain either no' cyanogen at all or littlelcyanogen and in spite of this possess a great cementing penetration, ifas a carbonaceous agent a carbon is used to which there have beenvimparted by previous physical or chemical'treatment, special propertiesexpediting the process of cementation.

Upto the present time it had not been possible to incorporate in thebath a quantity of carbon suilicient to obtain a deep cementation. IthasY been found that the kind of carbon which has so far been used incementing baths would separate from the salts and rise to the surface ofthe bath,

0 where it will burn quickly through the action of the oxygen of theair. In consequence of this no -intensive carburization of thework-,piece could` be attained.

, My invention is based upon the discovery that Y 45 a deep cementingeiect can be attained by means of carbon which is especially suitablefor this purpose, that is a carbon which has been subiected to aphysical or chemical' treatment with a view to activating said carbon,thereby reducing 50. its combustibility either in the manner describedin the German Patents 453,972 of Decemberg28, 1927, 466,358 of October5, 1928, and 488,669 of January 3, 1930 or in some other way.

Such carbons are termed herein and inthe aforementioned manner whichcontain only from 55 55 claims acuvatedcarbon of 10W ombusubiuty.

These carbons, upon being subjected to the lfull flame of a Bunsenburner for a period of two hours, leave a residue of non-combustibles ofat l' least 59% by weight of the original sample as distinguished fromthe ordinary activated c ar- 5 bon, which, uponsubjection to the sametests, leaves a considerably smaller percentage o! noncombustibles.

In accordance with the disclosure of 'German Patent No'. 453,972,'ordinary carbon from any 1b source isfheated to glowing in a suitablevessel with porous or gas-permeable walls, and thereafter submittedwhile glowing to the action of f oxygen or oxygen-containing gasespassed through the carbonmass or through the walls oi 15 said vessel.The German Patent No; 466,358 describes an improvement oi' the processof German Patent No. 453,972 by which everiless combustible activatedcarbon is prepared by treating granular carbon from any sourcel with awater- 20 glass solution followed by precipitation of the i silicio acidby the action of acids prior to the treatment pi thecarbon as dcribed inthe main German Patent No. 453,972. An activated carbon product having'asilicic acid skeleton is pro-r 2 5 i duced which possesses greatmechanical strength and may be used advantageously in chemical reactionswithout losing its shape. The 'German Patent No. 488,669describes'another method for manufacturing a-highly activated carbon oflow 30 combustibility. The carbon is treatedwith inorganic substances insolution, or as colloids', which substances exert acombustion-decreasing in- `fluence, and are precipitated as insolubleoxides by a carbonization process. Priorto carboniza- 3 5 tion, othersubstances are also added, such as zinc chloride or phosphoric acid toincreasethe activity of thevcarbon.` It willbe noted that all of theseprocesses produce anactivated carbon of low combustibility which hasproved, in accordance with the lpresent invention. to give novel f andunexpected results when Aemployed in c einenting salt baths. j v

` When using carbon or this kind it will be possible to incorporate aquantity of carbon amountlng to as much as 10% in the cementing bath andthereby to obtain an exceptional penetration. It will also be possiblewhen using l such cementing baths to work at temperatures above 900 C.which will greatly expedite the cementing process but could not be usedeasily in the present c einenting baths, as the latter are liable`toundergo decomposition at these temperatures. I have succeeded in makingup salt baths in the to 98% of sodium cyanide.

4 to 6% of pure cyanogen and in spite of this will eil'ect a.cementation which heretofore could hardly be attained with saltscontaining from The poisonous and dangerous character of these saltbaths will thus be quite considerably reduced with the result that.these new baths do not involve more danger than many machines andprocesses used in the modern indust-ry. In addition to this, such bathsare materially cheaper than salt baths having a high content of cyanide.

The baths may be made up in the usual manner and, besides chlorides,also carbonates and alkalies may be used. The cyanide compoundscontained in the baths may consist of sodium cyanide or potassiumcyanide, potassium ferrocyanide, calcium cyanamide and so forth.

'I'he following two examples are given to show how the new salt bathsmay be composed.

On the basis of experiments I have ascertained that with properlycomposed baths there will be an excellent cementation, also in case -oisolid cementing agents, if at at the same time activated carbon of lowcombustibility is used in considerable quantities.

Example 3 A Per cent Ordinary carbon 85 Potassium ferro-cyanide 5Activated carbon of low combustibility 5 Carbonate of barium 5li'roample 4 Per cent Ordinary carbon Activated carbon of lowcombustibility 5 Carbonate of barium 5 I have further ,found that thetime required for the cementing process may be considerably reduced, ii'the cementing bath is closed hermetically and kept under pressure.

In the drawing I have shown-in diagrammatic vertical section anapparatus which is suitable for carrying out my novel process'iorcementing steel and iron under pressure.

'I'he container I may be hermetically closed by -.means of a coverl 2.and packings 3'; as indicated in the drawing. The gases'whicharesbeing'de.- veloped at the cementing temperatures will cause anover-pressure to arise within the container I which over-pressure may beregulated by'means of the valve 4, 5 and controlled by 3a pressure gauge8. .d The work-piece 1 to be subjected to the cementing process issuspended within the container I and kept immersed in the bath 8 withinthe container I.- As cementing baths with which -the process oicementing maybecan'ied out under pressurethere may be used baths of theai'orementioned kindkas welly as allother cementing baths which hadheretofore been used, especially also `cyanogen containing cementingagents known in commerce under various trade-marks or the variouscyanide hardening compounds sold under the name of their manufacturers.5

I claim:

1. An iron and steel cementing bath composition, molten at cementingtemperatures and containing material capable of supplying carbon to themetal at said temperatures, comprising an 10 alkali metal cyanide in theneighborhood of 8%, sodium chloride in the neighborhood of- 62% to 65%,potassium chloride in the neighborhood oi I 18% to '19%, and anactivated carbon of low combustibility in the neighborhood of 8%'. 15

2. .An iron and steel cementing bath composition, molten at cementingtemperatures,and containing material capabl of supplying carbon to themetal at said temperatures, comprising a salt inert to th'e iron andsteel molten at vcementing 20 temperatures as the major ingredient ofsaid composition, and at least 4% of activated carbon of lowcombustibility, the lastl named ingredient supplying carbon to the metalat cementing temperatures. 25

3. An iron and steel cementing bath composition, molten at cementingtemperatures and containing material capable oi supplying carbon to themetal at said temperatures, comprising a salt inert t0 the iron andsteel molten at cementing 30 temperatures as the major ingredient ofsaid composition, a cyanide compound and. at least 4% of activatedcarbon of low ,combustibilitm the last named ingredients supplyingcarbon to the metal at cementing temperatures. *.5

4. An iron and steel cementing bath composition, molten at cementingtemperatures and containing material capable oi' supply carbon to themetal at said temperatures. comprising a mixture of salts inert to theiron and steel molten at 40 cementing temperatures' as the majoringredient of said composition, alkali metal cyanide and atleast 4% ofactivated carbon of low combustibility, the last named ingredientssupplying carbon to the metal at cementing temperatures. '4

5. An iron and steel cementing bath composition, molten at cementingtemperatures and containing mterial capable 0i' supplying carbon to themetal at said temperatures, comprising a salt inert to the iron andsteel molten at cementing 50 temperatures as the major ingredient oi.'said composition, alkali metal cyanide in the neighbor- Y borhood of 8%and activated carbon of low combustibinty between 4% and 10%.the1astnamed 5 ingredients supplying carbon to the metal at cementingtemperatures. 7. An iron and. steel cementing bath composition, moltenat cementing temperatures and containing material capable of supplyingcarbon 70 to the metal at said temperatures, comprising a salt inert tothe iron and steel molten at cementing temperatures as the majoringredient of said composition, alkali metal cyanide in the neighborhoodoi 8% and activated carbon of low com- 75 borhood of 2%, and causticsoda in the neighbor-l bustibility in the neighborhood of 8%, the lastnamed ingredients supplying carbon to the metal at cementingtemperatures.

8. An iron and steel cementing bath composition, molten at cementingtemperatures and containing material capable of supplying carbon to themetal at said temperatures, comprising an alkali metal cyanide in theneighborhood of 8%, sodium chloride in the neighborhood of 62%, po-

tassium'chloride in the neighborhood of 18%, ac-

tivated carbon of low combustibility in the neighborhoodof 8%, bariumcarbonate in the neigh- 3 temperatures as the major ingredient of saidcomposition, and at least four percent or activated carbon of lowcombustibility .containing inorganic material within its pores, the saidactivated carbon supplying carbon to the metal at cementing'temperatures. n

10. An iron and steel cementing bath componition. molten at cementingtemperatures, and containing material capable of supplying carbon to themetal at said temperatures, comprising a salt" 10 inert to the iron andsteel molten at cementing temperatures as the major ingredient of saidcomposition, and at least four percentof activated carbon of lowcombustibility having a silicic acid skeleton, the said activatedcarbonsupply- 15 ing carbon to the metal at cementing temperav tures.

